Aggressive impulsive behavior is a normal characteristic of pre-school children that dissipates during middle-childhood as they develop more advanced self-regulation abilities. However, many young children with early behavioral self-regulation problems show continuity of aggressive behavior into middle childhood. Efforts will be made in this project to identify the developmental and ecological risk factors that differentiate children who show stability of behavior problems from those who have externalizing problems early but not later with specific attention to gender differences. 120 male and 120 female children will be recruited into a longitudinal study and assessed when they are 3-years old and again in the second semester of kindergarten when they will be about 5-1/2. At each age observations and testing of child and social interactions will take place in the home, in the laboratory, in the classroom, and in a group interaction setting with unfamiliar peers. In addition during the second wave the kindergarten children will be observed interacting with their familiar classmates. Cognitive-verbal skills, "theory of mind," moral development, affect and attention control, and activity level will be assessed as component subprocesses of self-regulation that influence aggressive behavior at each age. In turn, parent-child interaction and social risk factors will be assessed as influences on both persistent maladjustment and the subprocesses of self-regulation that underlay the maladjustment. Linear, additive, and transactional models will be tested of the linkage between early and later behavior problems. In the transactional model, Wave I child regulation problems are predicted to negatively affect Wave II parent and peer interaction behavior that will, in turn, exacerbate Wave II externalizing problem behavior.